The old AMA engine class codes was for competition catagory purposes not used for many years now with the exception of SAM vintage oldtimer contests and the Vintage Stunt Championships for vintage controlline.

The catatgories were changed over the years to meet the needs of what was being flown at the time The original classes were: A -.05 to .20, B - .20 to .30, C - .30 to .65. with the advent of the micro glow engines in 1947 the 1/2A up to .05 class was added and later class C was broken down with class D also.

With 1/2A class limit being at .05 this is the reason most 1/2A engines were designed at .049. Another example of this with the limit for class A at .20, most were designed at .19 as were most class B engines were .29's.

In the late forties or possibly early fifties the (pulse) Jet class was added.

When Cox originally came out with the .010 with that huge three inch prop there was talk of a Quarter A class but this may not have become fact even though the expression 1/4A did find its way into the venacular of the time.


John